An epoxy resin has been employed in a variety of fields because of the excellence in heat resistance, mechanical strength, and electric properties, etc. As the epoxy resin, although there are usually employed a diglycidyl ether of bisphenol A and a phenol novolak type one, particularly, in a field in which heat resistance is required, there have been known an epoxide of a polyphenol obtained by a condensation reaction of hydroxybenzaldehydes with phenols and a composition thereof (JP-A-57141419 Official Gazette), and an resin composition containing an epoxide of a polyphenol obtained from unsaturated aliphatic aldehydes such as croton aldehyde (JP-A-61168620 Official Gazette). However, although the epoxy resin compositions are excellent in heat resistance, there are problems that insulation properties lower in the case of employing as electric insulators, and cracks are caused in a package in the case of employing as encapsulants for semiconductors because of a high water absorptive property.
On the other hand, for the purpose of improving water resistance, there is proposed an epoxy resin composition (JP-A-61291615) having alicyclic structures in the molecule which is obtained from dicyclopentadiene.
However, in the epoxy resin composition, although water resistance is improved, heat resistance lowers and flame retardancy is poor, namely, there is a problem that it is not preferred in view of reliability at high temperature.